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Temporary lifetime extension through tuple struct and tuple variant constructors #140593

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d91eb54
Implement temporary lifetime extension for tuple ctors.
m-ou-se May 2, 2025
dec02c1
Update tests.
m-ou-se May 2, 2025
7c8251f
Add comment.
m-ou-se May 2, 2025
2dce0dc
Add tests.
m-ou-se May 3, 2025
c57879c
Add test for temporary lifetime extension in `Self()` syntax.
m-ou-se May 7, 2025
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21 changes: 14 additions & 7 deletions compiler/rustc_hir_analysis/src/check/region.rs
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Expand Up @@ -10,6 +10,7 @@ use std::mem;

use rustc_data_structures::fx::FxHashMap;
use rustc_hir as hir;
use rustc_hir::def::{CtorKind, DefKind, Res};
use rustc_hir::def_id::DefId;
use rustc_hir::intravisit::{self, Visitor};
use rustc_hir::{Arm, Block, Expr, LetStmt, Pat, PatKind, Stmt};
Expand Down Expand Up @@ -752,13 +753,19 @@ fn resolve_local<'tcx>(
record_rvalue_scope_if_borrow_expr(visitor, arm.body, blk_id);
}
}
hir::ExprKind::Call(..) | hir::ExprKind::MethodCall(..) => {
// FIXME(@dingxiangfei2009): choose call arguments here
// for candidacy for extended parameter rule application
}
hir::ExprKind::Index(..) => {
// FIXME(@dingxiangfei2009): select the indices
// as candidate for rvalue scope rules
hir::ExprKind::Call(func, args) => {
// Recurse into tuple constructors, such as `Some(&temp())`.
//
// That way, there is no difference between `Some(..)` and `Some { 0: .. }`,
// even though the former is syntactically a function call.
if let hir::ExprKind::Path(path) = &func.kind
&& let hir::QPath::Resolved(None, path) = path
&& let Res::SelfCtor(_) | Res::Def(DefKind::Ctor(_, CtorKind::Fn), _) = path.res
{
for arg in args {
record_rvalue_scope_if_borrow_expr(visitor, arg, blk_id);
}
}
}
_ => {}
}
Expand Down
1 change: 0 additions & 1 deletion src/tools/tidy/src/issues.txt
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Expand Up @@ -760,7 +760,6 @@ ui/consts/issue-46553.rs
ui/consts/issue-47789.rs
ui/consts/issue-50439.rs
ui/consts/issue-52023-array-size-pointer-cast.rs
ui/consts/issue-54224.rs
ui/consts/issue-54348.rs
ui/consts/issue-54387.rs
ui/consts/issue-54582.rs
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2 changes: 1 addition & 1 deletion tests/ui/consts/const-mut-refs/mut_ref_in_final.rs
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Expand Up @@ -18,7 +18,7 @@ const B: *mut i32 = &mut 4; //~ ERROR mutable references are not allowed
const B2: Option<&mut i32> = None;

// Not ok, can't prove that no mutable allocation ends up in final value
const B3: Option<&mut i32> = Some(&mut 42); //~ ERROR temporary value dropped while borrowed
const B3: Option<&mut i32> = Some(&mut 42); //~ ERROR mutable references are not allowed

const fn helper(x: &mut i32) -> Option<&mut i32> { Some(x) }
const B4: Option<&mut i32> = helper(&mut 42); //~ ERROR temporary value dropped while borrowed
Expand Down
10 changes: 3 additions & 7 deletions tests/ui/consts/const-mut-refs/mut_ref_in_final.stderr
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Expand Up @@ -4,15 +4,11 @@ error[E0764]: mutable references are not allowed in the final value of constants
LL | const B: *mut i32 = &mut 4;
| ^^^^^^

error[E0716]: temporary value dropped while borrowed
--> $DIR/mut_ref_in_final.rs:21:40
error[E0764]: mutable references are not allowed in the final value of constants
--> $DIR/mut_ref_in_final.rs:21:35
|
LL | const B3: Option<&mut i32> = Some(&mut 42);
| ----------^^-
| | | |
| | | temporary value is freed at the end of this statement
| | creates a temporary value which is freed while still in use
| using this value as a constant requires that borrow lasts for `'static`
| ^^^^^^^

error[E0716]: temporary value dropped while borrowed
--> $DIR/mut_ref_in_final.rs:24:42
Expand Down
12 changes: 0 additions & 12 deletions tests/ui/consts/issue-54224.rs
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23 changes: 0 additions & 23 deletions tests/ui/consts/issue-54224.stderr
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3 changes: 2 additions & 1 deletion tests/ui/consts/promote-not.rs
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Expand Up @@ -3,10 +3,11 @@
#![allow(unconditional_panic)]

use std::cell::Cell;
use std::convert::identity;
use std::mem::ManuallyDrop;

// We do not promote mutable references.
static mut TEST1: Option<&mut [i32]> = Some(&mut [1, 2, 3]); //~ ERROR temporary value dropped while borrowed
static mut TEST1: &mut [i32] = identity(&mut [1, 2, 3]); //~ ERROR temporary value dropped while borrowed

static mut TEST2: &'static mut [i32] = {
let x = &mut [1,2,3]; //~ ERROR temporary value dropped while borrowed
Expand Down
66 changes: 33 additions & 33 deletions tests/ui/consts/promote-not.stderr
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@@ -1,15 +1,15 @@
error[E0716]: temporary value dropped while borrowed
--> $DIR/promote-not.rs:9:50
--> $DIR/promote-not.rs:10:46
|
LL | static mut TEST1: Option<&mut [i32]> = Some(&mut [1, 2, 3]);
| ----------^^^^^^^^^-
| | | |
| | | temporary value is freed at the end of this statement
| | creates a temporary value which is freed while still in use
| using this value as a static requires that borrow lasts for `'static`
LL | static mut TEST1: &mut [i32] = identity(&mut [1, 2, 3]);
| --------------^^^^^^^^^-
| | | |
| | | temporary value is freed at the end of this statement
| | creates a temporary value which is freed while still in use
| using this value as a static requires that borrow lasts for `'static`

error[E0716]: temporary value dropped while borrowed
--> $DIR/promote-not.rs:12:18
--> $DIR/promote-not.rs:13:18
|
LL | let x = &mut [1,2,3];
| ^^^^^^^ creates a temporary value which is freed while still in use
Expand All @@ -19,7 +19,7 @@ LL | };
| - temporary value is freed at the end of this statement

error[E0716]: temporary value dropped while borrowed
--> $DIR/promote-not.rs:34:29
--> $DIR/promote-not.rs:35:29
|
LL | let _x: &'static i32 = &unsafe { U { x: 0 }.x };
| ------------ ^^^^^^^^^^^^^^^^^^^^^^^ creates a temporary value which is freed while still in use
Expand All @@ -29,7 +29,7 @@ LL | };
| - temporary value is freed at the end of this statement

error[E0716]: temporary value dropped while borrowed
--> $DIR/promote-not.rs:40:29
--> $DIR/promote-not.rs:41:29
|
LL | let _val: &'static _ = &(Cell::new(1), 2).1;
| ---------- ^^^^^^^^^^^^^^^^^ creates a temporary value which is freed while still in use
Expand All @@ -39,7 +39,7 @@ LL | };
| - temporary value is freed at the end of this statement

error[E0493]: destructor of `String` cannot be evaluated at compile-time
--> $DIR/promote-not.rs:47:14
--> $DIR/promote-not.rs:48:14
|
LL | let x = &String::new();
| ^^^^^^^^^^^^^ the destructor for this type cannot be evaluated in constants
Expand All @@ -48,7 +48,7 @@ LL | };
| - value is dropped here

error[E0716]: temporary value dropped while borrowed
--> $DIR/promote-not.rs:59:33
--> $DIR/promote-not.rs:60:33
|
LL | let _x: &'static u32 = &mk_panic();
| ------------ ^^^^^^^^^^ creates a temporary value which is freed while still in use
Expand All @@ -58,7 +58,7 @@ LL | }
| - temporary value is freed at the end of this statement

error[E0716]: temporary value dropped while borrowed
--> $DIR/promote-not.rs:21:32
--> $DIR/promote-not.rs:22:32
|
LL | let _x: &'static () = &foo();
| ----------- ^^^^^ creates a temporary value which is freed while still in use
Expand All @@ -68,7 +68,7 @@ LL | }
| - temporary value is freed at the end of this statement

error[E0716]: temporary value dropped while borrowed
--> $DIR/promote-not.rs:29:29
--> $DIR/promote-not.rs:30:29
|
LL | let _x: &'static i32 = &unsafe { U { x: 0 }.x };
| ------------ ^^^^^^^^^^^^^^^^^^^^^^^ creates a temporary value which is freed while still in use
Expand All @@ -78,7 +78,7 @@ LL | }
| - temporary value is freed at the end of this statement

error[E0716]: temporary value dropped while borrowed
--> $DIR/promote-not.rs:65:29
--> $DIR/promote-not.rs:66:29
|
LL | let _val: &'static _ = &(Cell::new(1), 2).0;
| ---------- ^^^^^^^^^^^^^^^^^ creates a temporary value which is freed while still in use
Expand All @@ -89,7 +89,7 @@ LL | }
| - temporary value is freed at the end of this statement

error[E0716]: temporary value dropped while borrowed
--> $DIR/promote-not.rs:66:29
--> $DIR/promote-not.rs:67:29
|
LL | let _val: &'static _ = &(Cell::new(1), 2).1;
| ---------- ^^^^^^^^^^^^^^^^^ creates a temporary value which is freed while still in use
Expand All @@ -100,7 +100,7 @@ LL | }
| - temporary value is freed at the end of this statement

error[E0716]: temporary value dropped while borrowed
--> $DIR/promote-not.rs:69:29
--> $DIR/promote-not.rs:70:29
|
LL | let _val: &'static _ = &(1/0);
| ---------- ^^^^^ creates a temporary value which is freed while still in use
Expand All @@ -111,7 +111,7 @@ LL | }
| - temporary value is freed at the end of this statement

error[E0716]: temporary value dropped while borrowed
--> $DIR/promote-not.rs:70:29
--> $DIR/promote-not.rs:71:29
|
LL | let _val: &'static _ = &(1/(1-1));
| ---------- ^^^^^^^^^ creates a temporary value which is freed while still in use
Expand All @@ -122,7 +122,7 @@ LL | }
| - temporary value is freed at the end of this statement

error[E0716]: temporary value dropped while borrowed
--> $DIR/promote-not.rs:71:29
--> $DIR/promote-not.rs:72:29
|
LL | let _val: &'static _ = &((1+1)/(1-1));
| ---------- ^^^^^^^^^^^^^ creates a temporary value which is freed while still in use
Expand All @@ -133,7 +133,7 @@ LL | }
| - temporary value is freed at the end of this statement

error[E0716]: temporary value dropped while borrowed
--> $DIR/promote-not.rs:72:29
--> $DIR/promote-not.rs:73:29
|
LL | let _val: &'static _ = &(i32::MIN/-1);
| ---------- ^^^^^^^^^^^^^ creates a temporary value which is freed while still in use
Expand All @@ -144,7 +144,7 @@ LL | }
| - temporary value is freed at the end of this statement

error[E0716]: temporary value dropped while borrowed
--> $DIR/promote-not.rs:73:29
--> $DIR/promote-not.rs:74:29
|
LL | let _val: &'static _ = &(i32::MIN/(0-1));
| ---------- ^^^^^^^^^^^^^^^^ creates a temporary value which is freed while still in use
Expand All @@ -155,7 +155,7 @@ LL | }
| - temporary value is freed at the end of this statement

error[E0716]: temporary value dropped while borrowed
--> $DIR/promote-not.rs:74:29
--> $DIR/promote-not.rs:75:29
|
LL | let _val: &'static _ = &(-128i8/-1);
| ---------- ^^^^^^^^^^^ creates a temporary value which is freed while still in use
Expand All @@ -166,7 +166,7 @@ LL | }
| - temporary value is freed at the end of this statement

error[E0716]: temporary value dropped while borrowed
--> $DIR/promote-not.rs:75:29
--> $DIR/promote-not.rs:76:29
|
LL | let _val: &'static _ = &(1%0);
| ---------- ^^^^^ creates a temporary value which is freed while still in use
Expand All @@ -177,7 +177,7 @@ LL | }
| - temporary value is freed at the end of this statement

error[E0716]: temporary value dropped while borrowed
--> $DIR/promote-not.rs:76:29
--> $DIR/promote-not.rs:77:29
|
LL | let _val: &'static _ = &(1%(1-1));
| ---------- ^^^^^^^^^ creates a temporary value which is freed while still in use
Expand All @@ -188,7 +188,7 @@ LL | }
| - temporary value is freed at the end of this statement

error[E0716]: temporary value dropped while borrowed
--> $DIR/promote-not.rs:77:29
--> $DIR/promote-not.rs:78:29
|
LL | let _val: &'static _ = &([1,2,3][4]+1);
| ---------- ^^^^^^^^^^^^^^ creates a temporary value which is freed while still in use
Expand All @@ -199,7 +199,7 @@ LL | }
| - temporary value is freed at the end of this statement

error[E0716]: temporary value dropped while borrowed
--> $DIR/promote-not.rs:81:29
--> $DIR/promote-not.rs:82:29
|
LL | let _val: &'static _ = &TEST_DROP;
| ---------- ^^^^^^^^^ creates a temporary value which is freed while still in use
Expand All @@ -210,7 +210,7 @@ LL | }
| - temporary value is freed at the end of this statement

error[E0716]: temporary value dropped while borrowed
--> $DIR/promote-not.rs:83:29
--> $DIR/promote-not.rs:84:29
|
LL | let _val: &'static _ = &&TEST_DROP;
| ---------- ^^^^^^^^^^ creates a temporary value which is freed while still in use
Expand All @@ -221,7 +221,7 @@ LL | }
| - temporary value is freed at the end of this statement

error[E0716]: temporary value dropped while borrowed
--> $DIR/promote-not.rs:83:30
--> $DIR/promote-not.rs:84:30
|
LL | let _val: &'static _ = &&TEST_DROP;
| ---------- ^^^^^^^^^ creates a temporary value which is freed while still in use
Expand All @@ -232,7 +232,7 @@ LL | }
| - temporary value is freed at the end of this statement

error[E0716]: temporary value dropped while borrowed
--> $DIR/promote-not.rs:86:29
--> $DIR/promote-not.rs:87:29
|
LL | let _val: &'static _ = &(&TEST_DROP,);
| ---------- ^^^^^^^^^^^^^ creates a temporary value which is freed while still in use
Expand All @@ -243,7 +243,7 @@ LL | }
| - temporary value is freed at the end of this statement

error[E0716]: temporary value dropped while borrowed
--> $DIR/promote-not.rs:86:31
--> $DIR/promote-not.rs:87:31
|
LL | let _val: &'static _ = &(&TEST_DROP,);
| ---------- ^^^^^^^^^ creates a temporary value which is freed while still in use
Expand All @@ -254,7 +254,7 @@ LL | }
| - temporary value is freed at the end of this statement

error[E0716]: temporary value dropped while borrowed
--> $DIR/promote-not.rs:89:29
--> $DIR/promote-not.rs:90:29
|
LL | let _val: &'static _ = &[&TEST_DROP; 1];
| ---------- ^^^^^^^^^^^^^^^ creates a temporary value which is freed while still in use
Expand All @@ -265,7 +265,7 @@ LL | }
| - temporary value is freed at the end of this statement

error[E0716]: temporary value dropped while borrowed
--> $DIR/promote-not.rs:89:31
--> $DIR/promote-not.rs:90:31
|
LL | let _val: &'static _ = &[&TEST_DROP; 1];
| ---------- ^^^^^^^^^ - temporary value is freed at the end of this statement
Expand All @@ -274,7 +274,7 @@ LL | let _val: &'static _ = &[&TEST_DROP; 1];
| type annotation requires that borrow lasts for `'static`

error[E0716]: temporary value dropped while borrowed
--> $DIR/promote-not.rs:98:26
--> $DIR/promote-not.rs:99:26
|
LL | let x: &'static _ = &UnionWithCell { f1: 0 };
| ---------- ^^^^^^^^^^^^^^^^^^^^^^^ creates a temporary value which is freed while still in use
Expand Down
4 changes: 2 additions & 2 deletions tests/ui/coroutine/auto-trait-regions.rs
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Expand Up @@ -43,8 +43,8 @@ fn main() {
// Disallow impls which relates lifetimes in the coroutine interior
let gen = #[coroutine] move || {
let a = A(&mut true, &mut true, No);
//~^ ERROR temporary value dropped while borrowed
//~| ERROR temporary value dropped while borrowed
//~^ ERROR borrow may still be in use when coroutine yields
//~| ERROR borrow may still be in use when coroutine yields
yield;
assert_foo(a);
};
Expand Down
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